In recent years, the amount of data transmitted over a wireless communication network is being increased quickly as various devices such as smart phones or tablet PCs requiring machine-to-machine (M2M) communication and high data transmission appear and spread. To meet a high amount of data transmission as required, technologies for efficiently using a broader frequency band such as carrier aggregation (CA) and cognitive radio (CR) and multi-antenna and multi-base station cooperative transmission technologies for raising data capacity in a limited frequency band are gaining more popularity.
Wireless communication networks are being evolved towards higher density of nodes that may access users' surroundings. Here, the ‘nodes’ physically mean antennas or antenna groups spaced apart from each other at a predetermined distance in the distributed antenna system (DAS) but are not limited thereto while being instead expanded to a broader meaning. In other words, a node may be a picocell base station (PeNB), a home base station (HeNB), an RRH (Remote Radio Head), an RRU (Remote Radio Unit), a relay station, or a distributed antenna (group).
A wireless communication system having a higher density of nodes may show higher system performance thanks to inter-node cooperation. That is, rather than operating as an independent base station without cooperation, when managed in transmission/reception by one control station to operate as an antenna or antenna group in a cell, each node may show more excellent system performance. Hereinafter, the wireless communication system including plural nodes is referred to as a multi-node system.
In this multi-node system, as the nodes are distributed arranged or according to transmission power of each node or whether there is an obstacle, the channel status between each node and a terminal may be sharply varied. For example, eight nodes may be controlled by a base station, and each node may have one transmission antenna. In such multi-node system, the eight nodes may be distributed and arranged to be spaced apart from each other at a predetermined distance. At this case, according to the position of the terminal, only four nodes may show a channel status of a predetermined value or more while the remaining four nodes may show a channel status of less than the specific value.
There is a need for a signal transmission method and apparatus considering the characteristics of the multi-node system.